Java Adapter Classes

Java adapter classes provide the default implementation of listener interfaces. If you inherit the adapter class, you will not be forced to provide the implementation of all the methods of listener interfaces. So it saves code.

Pros of using Adapter classes:

It assists the unrelated classes to work combinedly.
It provides ways to use classes in different ways.
It increases the transparency of classes.
It provides a way to include related patterns in the class.
It provides a pluggable kit for developing an application.
It increases the reusability of the class.

The adapter classes are found in java.awt.event, java.awt.dnd and javax.swing.event packages. The Adapter classes with their corresponding listener interfaces are given below.

java.awt.event Adapter classes

Adapter class	Listener interface
WindowAdapter	WindowListener
KeyAdapter	KeyListener
MouseAdapter	MouseListener
MouseMotionAdapter	MouseMotionListener
FocusAdapter	FocusListener
ComponentAdapter	ComponentListener
ContainerAdapter	ContainerListener
HierarchyBoundsAdapter	HierarchyBoundsListener

java.awt.dnd Adapter classes

Adapter class	Listener interface
DragSourceAdapter	DragSourceListener
DragTargetAdapter	DragTargetListener

javax.swing.event Adapter classes

Adapter class	Listener interface
MouseInputAdapter	MouseInputListener
InternalFrameAdapter	InternalFrameListener

Java WindowAdapter Example

In the following example, we are implementing the WindowAdapter class of AWT and one its methods windowClosing() to close the frame window.

AdapterExample.java

  // importing the necessary libraries  import java.awt.*;    import java.awt.event.*;      public class AdapterExample {  // object of Frame        Frame f;    // class constructor      AdapterExample() {    // creating a frame with the title          f = new Frame (“Window Adapter”);    // adding the WindowListener to the frame  // overriding the windowClosing() method           f.addWindowListener (new WindowAdapter() {                public void windowClosing (WindowEvent e) {                    f.dispose();                }            });             // setting the size, layout and           f.setSize (400, 400);            f.setLayout (null);            f.setVisible (true);        }      // main method  public static void main(String[] args) {        new AdapterExample();    }    }    

Output:

Java MouseAdapter Example

In the following example, we are implementing the MouseAdapter class. The MouseListener interface is added into the frame to listen the mouse event in the frame.

MouseAdapterExample.java

  // importing the necessary libraries  import java.awt.*;    import java.awt.event.*;      // class which inherits the MouseAdapter class  public class MouseAdapterExample extends MouseAdapter {    // object of Frame class      Frame f;    // class constructor      MouseAdapterExample() {    // creating the frame with the title          f = new Frame (“Mouse Adapter”);    // adding MouseListener to the Frame          f.addMouseListener(this);       // setting the size, layout and visibility of the frame          f.setSize (300, 300);            f.setLayout (null);            f.setVisible (true);        }    // overriding the mouseClicked() method of the MouseAdapter class      public void mouseClicked (MouseEvent e) {    // creating the Graphics object and fetching them from the Frame object using getGraphics() method          Graphics g = f.getGraphics();    // setting the color of graphics object          g.setColor (Color.BLUE);    // setting the shape of graphics object          g.fillOval (e.getX(), e.getY(), 30, 30);        }      // main method  public static void main(String[] args) {        new MouseAdapterExample();    }    }    

Output:

Java MouseMotionAdapter Example

In the following example, we are implementing the MouseMotionAdapter class and its different methods to listen to the mouse motion events in the Frame window.

MouseMotionAdapterExample.java

  // importing the necessary libraries  import java.awt.*;    import java.awt.event.*;    // class which inherits the MouseMotionAdapter class  public class MouseMotionAdapterExample extends MouseMotionAdapter {     // object of Frame class      Frame f;    // class constructor      MouseMotionAdapterExample() {    // creating the frame with the title          f = new Frame (“Mouse Motion Adapter”);    // adding MouseMotionListener to the Frame          f.addMouseMotionListener (this);     // setting the size, layout and visibility of the frame          f.setSize (300, 300);            f.setLayout (null);            f.setVisible (true);        }    // overriding the mouseDragged() method   public void mouseDragged (MouseEvent e) {    // creating the Graphics object and fetching them from the Frame object using getGraphics() method      Graphics g = f.getGraphics();    // setting the color of graphics object      g.setColor (Color.ORANGE);    // setting the shape of graphics object      g.fillOval (e.getX(), e.getY(), 20, 20);    }    public static void main(String[] args) {        new MouseMotionAdapterExample();    }    }    

Output:

Java KeyAdapter Example

In the following example, we are implementing the KeyAdapter class and its method.

KeyAdapterExample.java

  // importing the necessary libraries  import java.awt.*;    import java.awt.event.*;    // class which inherits the KeyAdapter class  public class KeyAdapterExample extends KeyAdapter {    // creating objects of Label, TextArea and Frame      Label l;        TextArea area;        Frame f;    // class constructor      KeyAdapterExample() {    // creating the Frame with title          f = new Frame (“Key Adapter”);    // creating the Label          l = new Label();    // setting the location of label           l.setBounds (20, 50, 200, 20);    // creating the text area          area = new TextArea();  // setting the location of text area            area.setBounds (20, 80, 300, 300);    // adding KeyListener to text area          area.addKeyListener(this);     // adding the label and text area to frame          f.add(l);  f.add(area);    // setting the size, layout and visibility of frame          f.setSize (400, 400);            f.setLayout (null);            f.setVisible (true);        }    // overriding the keyReleased() method       public void keyReleased (KeyEvent e) {    // creating the String object to get the text fromTextArea           String text = area.getText();    // splitting the String into words          String words[] = text.split (“\s”);    // setting the label text to print the number of words and characters of given string          l.setText (“Words: ” + words.length + ” Characters:” + text.length());        }      // main method      public static void main(String[] args) {            new KeyAdapterExample();        }    }    

Output:

Next TopicHow to close AWT Window in Java

Java Adapter Classes

Java Adapter Classes

Pros of using Adapter classes:

java.awt.event Adapter classes

java.awt.dnd Adapter classes

javax.swing.event Adapter classes

Java WindowAdapter Example

Java MouseAdapter Example

Java MouseMotionAdapter Example

Java KeyAdapter Example

Java Autoboxing and Unboxing

Java SequenceInputStream Class

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